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Good afternoon and merry X-mas to all bricksters. Hoping to get some input on rear brakes. Recently I did a complete rear brake job on a friend's '92 245. This included new e-brake hardware and shoes, new discs, pads, hardware, the works. E-brake properly adjusted. Every once in awhile she gets this low, moaning sound just before stopping. Thinking this was e-brake shoe drag, we have readjusted that, but to no avail. Could this be something else? A source has suggested that we need the "attenuator kit", which apparently eliminates vibration in calipers, or some such thing. I had never heard of such a thing, but a few days ago I stumbled across a 245 with large, triangular, rubber bumpers bolted in place back there pointing toward the ground. Does anyone have any information on this issue/part?
Thx,
Dave
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Brake moan: usually low frequency noise phenomenon <500Hz.
Typically generated at low speed and brake pressures < 7bar. Pads and disk stick momentarily and then release causing an excitation transmitted to suspension and beam. We often report in EU either the beam vibrating or the tie blade. Brake manufacturers usually provide add-on component such a damper to cancel out the vibration. Indeed, the damper vibrates at the same frequency as the beam for instance but out of phase, therefore reducing the energy transmitted to the axle.
Dampeer is usually mounted onto the guiding or locking pin of the housing.
The best thing would be to use a reinforced spindle or a thicker beam section, but this would cost to much to car manufacturers.
Cheers
Laurent
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happy christmas:
i have had simliar problems with rear brakes which turned out to be not enough clearance between the pads as they slide on the pins after the brakes are depressed. i have found the easiest way to resolve the prolem was to remove the pads and grind down slightly metal edges on which the pads are affixed.
moan went away.
normaly this happens once the pads have beeen in their a while and dirt gets lodged between the pad edges and caliper walls.
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Dave:
If you went with aftermarket pads, make sure the leading and trailing edges of the pads are beveled, if not, put the on the belt sander and add the bevel to the pad material.
Also make sure the pad shim plates are in place, if they are not, all kinds of noises can result.
Finally, check for axle bearing play... see if you can move the axle up and down, don't know what the measurement limits are though.
jorrell
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92 245 245K miles, IPD'd to the hilt, 06 XC70, 00 Eclipse custom Turbo setup...currently in pieces
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Thanks Jorrell. We have beveled edges. We have teflon shims and we have silicone grease on the hardware and other usual places. Noise only showed up after the work was done, so I don't think this is an axle issue, but for the record, are you suggesting we may have enough float for the e-brake shoes to be contacting the inside of the disc?
Any input on the rubber "insulators", or whatever they are under the axle?
thanks,
DS
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Necer had this issue, and just following you thought about the float causing E-brake rubbing.
Does this groan only happen when Braking while turning one direction or another? Just thinking that IF it is an Axle float issue, then it might only show up when you are turning slightly so the axle is forced outward. It just might help in Diagnosing the problem.
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'75 Jeep CJ5 345Hp ChevyPwrd, two motorcycles, '85 Pickup: The '89 Volvo is the newest vehicle I own. it wasn't Volvos safety , it was Longevity that sold me
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Thanks Tony. No, the issue is not related to turning, though I follow your logic. It only happens when the car is coming to a stop. That is, the last couple of miles per hour. After searching the brickboard for many months on the vibration attentuator issue, I finally, yesterday, stumbled across a post by searching for "tuning fork". Someone mentions the rubber insulator bolted to the bottom of the caliper and also comments that this problem is much more common on wagons. I'll have to find a set in a yard and examine exactly how it is they are affecting this. It's almost as if they are tuning out some sort of vibration if I understand correctly. Weird.
DS
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Aside from reading this thread, I never heard of this Rubber Isolator/insulator.
Good luck
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'75 Jeep CJ5 345Hp ChevyPwrd, two motorcycles, '85 Pickup: The '89 Volvo is the newest vehicle I own. it wasn't Volvos safety , it was Longevity that sold me
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I've been trying to find the post again all morning, but I think the search engine is down. Not to worry. I just came back from the AC shop where I had dropped off a '92 wagon last week. First thing I did when I got it home was crawl under the back (car only with us for a couple of weeks so far). Lo and behold, bolted to the underside of the caliper is a large, black, triangular shaped rubber bumper attached to a bracket. It points straight down. Looks like an upside-down bump stop. I can hardly believe it! Vovobub, wherever you are, I apologize for my doubts! This must be it. My daily driver is a '91 and it doesn't have this, nor have any of the other wagons that have crossed my driveway in the last couple of years. Nonetheless....
DS
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David:
Not sure about the add-on "isolators", personally, I have never heard of them. The only rubber parts below the axle that I am aware of are the Trailing Arm Bushings.
Just a guess here, but by chance did you change the rear dif fluid while you were at it? If yes, and this car has a posi rear end, you will need to add a friction modifier to the rear diff fluid. Posi rear ends are rare in these cars but I've had plenty of them moan if they are run on standard lube without modifier.
jorrell
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92 245 245K miles, IPD'd to the hilt, 06 XC70, 00 Eclipse custom Turbo setup...currently in pieces
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